PITCH, a term applied to a variety of resinous substances of a dark color and brilliant luster, obtained from the va rious kinds of tar produced in the de structive distillation of wood, coal, etc. In architecture, the rise or versed sine of an arch. In carpentry, the inclina tion of a roof. The common pitch has a rafter three-quarters the length of the span; the Gothic has a full pitch; the rafters being the length of the span; the Greek has a pitch 1,6 to 1/2 of the span; the Roman has a pitch from % to % of the span; and the Elizabethan has raf ters longer than the span.
In hydraulic engineering, in overshot water wheels the bucket-pitch is a circu lar line passing through the elbows of the buckets. The elbow is the junction of the floor and the arm, which together form the bucket. In machinery: (1) the distance between the threads of a screw measured on a line parallel to the axis. (2) The distance between the centers of two adjacent teeth in a cog wheel, measured on the pitch circle. (3) The pitch of a rivet is the distance apart from center to center. (4) The distance between the stays of marine and other steam boilers. In marine boilers it is usually from 12 to 18 inches. In mining, a lode or portion of a lode let out to men to work by the piece or by a percentage of the output.
In music, musical sounds give to the mind a feeling of acuteness or gravity according to the rapidity or slowness of the vibrations producing them; hence, the former are called acute or high, the latter grave or low. The absolute pitch of sounds is measured by giving the number of vibrations per second which produces a given sound, e. g., C = 528;
the relative pitch of sounds is described by giving the ratio of vibrations of the interval, e. g., a fifth is 2:3—that is, the higher sound of any interval of a fifth gives three vibrations, while the lower sound in the same time gives two. The determination of fixed pitch is purely arbitrary, and it has from time to time undergone great variations. In England we have high concert pitch C = about 540, more or less, and the medium pitch C = 528; on the Continent the French "diapason normal," C = 518, is being largely adopted. The official standard adopted in the United States during the world's fair was what is known as inter national or "French" pitch, which gives as a standard middle A with 435 vibra tions, though the majority of American upright pianos are tuned to high concert pitch.
In planes, the slant of a plane bit in its stock. In printing, one of the guide pins, which, in floor-cloth printing, an swers the purpose of the register points. In shipbuilding: (1) The pitch of the paddles is the distance between them, measured on the circle which passes through their centers. It is commonly from 1.6 to double their depth. (2) The pitch of a propeller-screw is the length, measured along the axis, of a complete turn. A gaining-pitch is one in which the pitch gradually increases from the leading to the following edge.